By the end of this year statistically valid samples will be completed enabling definitive comparisons to be made between larval and pupal periods and longevities for all five taxa in the virilis group of Drosophila. Two tropical species will be added to the study for contrast with temperate forms already under investigation. Diapause capacities will be established for all species in the group and a relation will be sought between longevity, capacity to diapause and ability to survive extended periods of time at subfreezing temperatures. If time permits, parallel investigations will begin on longevities and life cycle parameters of closely related species in the montana phylad of the virilis group.